Abstract
Shallow soil with low water availability is the key limiting factor for plant growth and reproduction in vulnerable karst regions. Annual herbs are pioneers adapted to these areas; however, little is known about the responses of their seeds and infructescence, and the germination of their offspring to these limited water and soil resources. In this study, we investigated how the seed and fruiting phenology plasticity and offspring seed germination rates of two annual Asteraceae herbs (Xanthium sibiricum and Bidens pilosa) respond to the harsh karst soil environment, by assessing the seed number, seed biomass and offspring seed germination rate. X. sibiricum and B. pilosa were grown under three soil thicknesses and three water availability levels in a full two-way randomized block design. The key results were as follows: (1) The number and biomass of progenies (infructescence and seeds) of X. sibiricum decreased with the decline of soil thickness and/or water availability (P <0.05). The infructescence and seed biomass of B. pilosa increased with the decline of water availability. (2) Seed quantity and seed biomass of X. sibiricum showed no correlation after their parents experienced resource reductions. A significant positive relationship between seed number and seed biomass was observed in B. pilosa (P <0.05). (3) The offspring seed germination rate of X. sibiricum did not change with the decrease of soil thickness under three levels of water treatment. However, the offspring seed germination rate of B. pilosa decreased significantly with the decrease of soil thickness under the control water level (P<0.05). The results show that X. sibiricum tends to improve its competitiveness by ensuring the quantity and quality of offspring in order to adapt to the shallow karst soils and dry karst habitats. In contrast, B. pilosa adapts to the unfavorable karst habitats by a risk-sharing strategy. B. pilosa produces more and bigger seeds to in an attempt to expand its survival range and escape from the unfavorable living environment, but this results in a lower seed number and germination rate of its progeny under the karst soil resource reduction.
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Claims 10
Claim · model-written summary
Xanthium sibiricum infructescence and seed number and biomass declined as soil thickness or water availability declined.
- Taxon
- X. sibiricum
Xanthium sibiricume0 - Treatment
- decline of soil thickness and/or water availabilitye0
- Outcome
- number and biomass of progenies (infructescence and seeds)e0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The number and biomass of progenies (infructescence and seeds) of X. sibiricum decreased with the decline of soil thickness and/or water availability (P <0.05).”
Claim · model-written summary
Bidens pilosa infructescence and seed biomass increased as water availability declined.
- Taxon
- B. pilosa
Bidens pilosae0 - Treatment
- decline of water availabilitye0
- Outcome
- infructescence and seed biomasse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The infructescence and seed biomass of B. pilosa increased with the decline of water availability.”
Claim · model-written summary
Xanthium sibiricum seed quantity and biomass were uncorrelated after parental resource reduction.
- Taxon
- X. sibiricumXanthium sibiricume0
- Organ / stage
- seede0
- Outcome
- Seed quantity and seed biomasse0
- Direction
- no correlatione0
- Qualifier
- after their parents experienced resource reductionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed quantity and seed biomass of X. sibiricum showed no correlation after their parents experienced resource reductions.”
Claim · model-written summary
Bidens pilosa seed number and seed biomass had a significant positive relationship.
- Taxon
- B. pilosaBidens pilosae0
- Organ / stage
- seede0
- Outcome
- seed number and seed biomasse0
- Direction
- positive relationshipe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A significant positive relationship between seed number and seed biomass was observed in B. pilosa (P <0.05).”
Claim · model-written summary
Xanthium sibiricum offspring seed germination rate did not change with decreasing soil thickness across water treatments.
- Taxon
- X. sibiricumXanthium sibiricume0
- Treatment
- decrease of soil thicknesse0
- Outcome
- offspring seed germination ratee0
- Direction
- did not changee0
- Qualifier
- under three levels of water treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The offspring seed germination rate of X. sibiricum did not change with the decrease of soil thickness under three levels of water treatment.”
Claim · model-written summary
Bidens pilosa offspring seed germination rate decreased with soil thickness under control water.
- Taxon
- B. pilosaBidens pilosae0
- Treatment
- decrease of soil thicknesse0
- Outcome
- offspring seed germination ratee0
- Direction
- decreasede0
- Qualifier
- under the control water levele0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the offspring seed germination rate of B. pilosa decreased significantly with the decrease of soil thickness under the control water level (P<0.05).”
Claim · model-written summary
The authors interpret Xanthium sibiricum as maintaining offspring quantity and quality to compete in shallow dry karst habitats.
- Taxon
- X. sibiricumXanthium sibiricume0
- Outcome
- improve its competitivenesse0
- Qualifier
- ensuring the quantity and quality of offspringe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“X. sibiricum tends to improve its competitiveness by ensuring the quantity and quality of offspring in order to adapt to the shallow karst soils and dry karst habitats.”
Claim · model-written summary
The authors interpret Bidens pilosa as using a risk-sharing strategy in unfavorable karst habitats.
- Taxon
- B. pilosaBidens pilosae0
- Outcome
- adapts to the unfavorable karst habitatse0
- Qualifier
- risk-sharing strategye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“B. pilosa adapts to the unfavorable karst habitats by a risk-sharing strategy.”
Claim · model-written summary
The authors interpret Bidens pilosa production of more and larger seeds as an attempt to expand its survival range.
- Taxon
- B. pilosaBidens pilosae0
- Outcome
- expand its survival range and escape from the unfavorable living environmente0
- Qualifier
- more and bigger seedse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“B. pilosa produces more and bigger seeds to in an attempt to expand its survival range and escape from the unfavorable living environment”
Claim · model-written summary
The authors report that this Bidens pilosa strategy results in lower progeny seed number and germination rate under resource reduction.
- Taxon
- B. pilosaBidens pilosae1
- Outcome
- seed number and germination rate of its progenye0
- Direction
- lowere0
- Setting
- karst soile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but this results in a lower seed number and germination rate of its progeny under the karst soil resource reduction.”
e1“B. pilosa produces more and bigger seeds”